1. Field of the Invention
The present invention relates to an angled offset ball type constant velocity joint for a vehicle, and more particularly, to an angled offset ball type constant velocity joint for a vehicle, which can enhance the strength of the joint by compensating for a contact surface pressure between an outer race groove and a ball while maintaining an outer diameter of an outer race by making an outer race rotation center and an inner race rotation center positioned to be symmetrical with respect to each other by an offset angle.
2. Description of the Related Art
In general, a joint functions to transmit rotational power (torque) between two rotation shafts which meet each other at an angle. In the case of a propeller shaft having a small power transmission angle, a hook joint, a flexible joint, etc. are used, and in the case of the driving shaft of a front wheel drive vehicle having a large power transmission angle, a constant velocity joint is used.
Since the constant velocity joint can reliably transmit power at a constant velocity even when an angle between a driving shaft and a driven shaft is large, the constant velocity joint is mainly used for the axle shaft of an independent suspension type front wheel drive vehicle. When viewed from a shaft, a tripod type constant velocity joint is provided to one end of the shaft which faces an engine (i.e., the inboard-side end), and a ball type joint is provided to the other end of the shaft which faces a tire (i.e., the outboard-side end).
FIG. 1 is a cross-sectional view illustrating conventional constant velocity joints, and FIG. 2 is a schematic view illustrating an external appearance of the conventional constant velocity joints shown in FIG. 1.
As shown in FIGS. 1 and 2, the conventional constant velocity joints comprise a tripod type constant velocity joint which is provided to the right end of a shaft 1 which faces an engine (the inboard-side end) and a ball type constant velocity joint provided to the left end of the shaft 1 which faces a tire (the outboard-side end).
The tripod type constant velocity joint installed on the right end of the shaft 1 (which faces the engine) comprises a housing 2 which transmits rotational power of the engine (not shown) and is defined with track grooves on the inner surface thereof, the shaft 1 which receives the rotational power from the housing 2 and rotates, a spider 3 which is disposed in the housing 2, is coupled to one end of the shaft 1 to connect the housing 2 and the shaft 1 with each other and is formed with three trunnions to be respectively inserted into the track grooves of the housing 2, needle rollers 6 which are arranged on the circumferential outer surface of each trunnion of the spider 3, inner rollers 5 each of which is arranged around the needle rollers 6 for each trunnion of the spider 3, outer rollers 4 each of which is installed on the circumferential outer surface of each inner roller 5 to reduce friction between the housing 2 and the shaft 1, a retainer ring 8 which is installed on the upper ends of the needle rollers 6 and of each inner roller 5, a boot 10 having one end which is connected to the housing 2 and the other end which is connected to the shaft 1, and clamping bands 11 and 12 which clamp both ends of the boot 10.
The ball type constant velocity joint installed on the left end of the shaft 1 (which faces the tire) comprises an inner race 15 which is installed on the left end of the shaft 1 to receive the rotational power from the tripod type constant velocity joint and to then rotate, an outer race 13 which is installed around the inner race 15, balls 16 for transmitting the rotational power of the inner race 15 to the outer race 13, a cage 14 for supporting the balls 16, a sensor ring 17 which is installed around the outer race 13, a boot 18 having one end which is connected to the shaft 1 and the other end which is connected to the outer race 13, and clamping bands 19 and 20 which clamp both ends of the boot 18.
A damper 21 is installed at the center of the shaft 1 using bands 22 and 23 and has a weight 211 installed in a body 212.
Hereafter, the operation of the conventional constant velocity joints constructed as mentioned above will be described.
As the rotational power outputted from an engine (not shown) is transmitted to the housing 2 through a transmission (not shown), the housing 2 is rotated. The rotational power of the housing 2 is transmitted to the spider 3 through the outer rollers 4, the inner rollers 5 and the needle rollers 6, and then the shaft 1 to which the spider 3 is coupled is rotated. The rotational power of the shaft 1 is transmitted to the outer race 13 through the inner race 15 and the balls 16, and then the wheel (not shown) connected to the outer race 13 is rotated.
In the tripod type constant velocity joint which is provided to the right end of the shaft 1 which faces the engine (i.e., the inboard-side end), as the outer rollers 4 slide in the track grooves of the housing 2, the rotation angle of the shaft 1 which is operationally associated with the outer rollers 4 is changed, so that a joint angle is created to follow the displacement of a vehicle. In the ball type constant velocity joint which is provided to the left end of the shaft 1 which faces the tire (i.e., the outboard-side end), the rotation angle of the outer race 13 is changed due to the presence of the balls 16, so that a joint angle is created to follow the displacement of the vehicle.
The boot 10 of the tripod type constant velocity joint and the boot 18 of the ball type constant velocity joint respectively function to enclose the tripod type constant velocity joint and the ball type constant velocity joint, so that the tripod type constant velocity joint and the ball type constant velocity joint are prevented from being contaminated by foreign substances.
In addition, when the torque outputted from the engine and the transmission through the shaft 1 to wheels, unbalanced rotation may occur at a certain rotation angle of the shaft 1 rotating at high speed, which may result in undesired vibrations and adversely affect the operation of a drive system. In order to prevent the undesired vibrations due to unbalanced rotation, the damper 2 installed at the center of the shaft 1 may prevent booming noises from occurring to the shaft 1 rotating at high speed due to the detrimental vibration frequency.
FIG. 3 is an exploded view illustrating a conventional ball type constant velocity joint for a vehicle, FIG. 4 is a perspective view of the conventional ball type constant velocity joint shown in FIG. 1, FIG. 5 is a cross-sectional view illustrating the conventional ball type constant velocity joint for a vehicle before a joint angle is created, and FIG. 6 is a cross-sectional view illustrating the conventional ball type constant velocity joint shown in FIG. 5 after a joint angle is created.
As shown in FIGS. 3 to 6, in the conventional ball type constant velocity joint for a vehicle, the ball 16 is fixed by the cage 14 and the inner race 15. During steering, the ball 16 is moved in the groove formed on a circumferential inner surface of the outer race 13 in a lengthwise direction.
A ball track (OBT) of the outer race 13 is formed to trace a radius R2 ranging from a rotation center r2 and a ball track (IBT) of the inner race 15 is formed to trace a radius R3 from a rotation center r3.
A funnel angle (f) formed between the rotation center r2 of the outer race ball track (OBT) and the rotation center r3 of the inner race ball track (IBT) at the center of the balls 36 is in a range of 12° to 15° for a 6-ball type joint and is in a range of 7° to 12° for a 8-ball type joint. The funnel angle (f) facilitates bending and rotating of the joint. Here, if the funnel angle (f) is not secured, the joint may get jammed and the efficiency of the joint may be lowered.
The rotation center r2 of the outer race ball track (OBT) and the rotation center r3 of the inner race ball track (IBT) are positioned to be parallel with each other by a constant offset amount R1 with regard to a joint rotation center r1. At the time of bending, the cage 14 and the balls 16 rotate by half a joint angle amount of the inner race 15, and the rotation center r2 of the outer race ball track (OBT) and the rotation center r3 of the inner race ball track (IBT) are rotated along a radius corresponding to the offset amount R1 with respect to the joint rotation center r1.
However, according to the trend toward lightweight and compact ball type constant velocity joints, the cage of the conventional ball type constant velocity joint may be subjected to intensified stress.